This study aims to investigate the effects of dynamic assessment on improving ELT learners of English as a foreign language at a large state university. The researchers followed the pre-test-treatment--post-test procedure in the study. The test type used in the assessment procedures was 'Retelling Story Test' type in which learners were provided with authentic news stories and expected to narrate the event in the story. The study involves both quantitative and qualitative data analysis. The statistical data were analyzed by Mann Whitney U-Test and Wilcoxon Sign Test. As for the qualitative data, responses to a student evaluation form were analyzed at the end of the whole procedure. The researchers found significance in the performances of control and experiment groups after the treatment program implemented for the latter group. The students also in the experiment group were able to maintain their success in transfer tests applied after the post-tests. Students were observed to be less dependent on the teacher's mediation in transfer tests, which proved the power of interactions in the students' Zone of proximal development. Furthermore, the qualitative data obtained from the student evaluation form revealed that learners found the assessment procedure beneficial.